1. Field of the Invention:
The present invention relates, in general, to vehicle transmission gear shifting mechanisms and, specifically, to transmission safety lock devices which prevent shifting of a transmission until certain predetermined safety-related conditions are met.
In vehicles provided with an automatic transmission, movement of a gear selector in the vehicle into any position of park, reverse, neutral or drive causes the transmission to be shifted through a linkage coupling the gear selector with the transmission into a gear ratio corresponding to park, reverse, neutral or drive. The vehicle engine operates independently of the transmission and can be operated when the transmission is in any of the park, reverse, neutral or drive modes. The operator controls movement of the vehicle in reverse or drive modes through the use of the vehicle accelerator and brake pedals.
However, some vehicle operators occasionally leave the vehicle for a short time with the engine operating and the transmission in park or neutral. When the engine is operating and the vehicle is unattended by an operator, a child can easily move the gear selector into reverse or drive thereby causing movement of the vehicle and creating the potential of property damage and bodily injury to the occupants of the vehicle and pedestrians or bystanders. Furthermore, design deficiencies, misalignment or wear in the transmission or the transmission shifting linkage occasionally causes transmissions to shift into reverse or drive without direct operator intervention. Again, this results in unattended and uncontrolled vehicle movement.
In order to prevent such unattended movement of a vehicle caused by the unintended shifting of the transmission into reverse or drive modes when the engine is running, several safety lock devices have been developed which prevent shifting of the transmission into drive or reverse modes until one or more safety-related conditions are met. Typically, such safety conditions require an intentional action by the operator of the vehicle which is difficult or impossible for a child. Generally, the known transmission safety lock devices employ stops or plungers which mechanically interlock with the vehicle gear selector and prevent movement of the gear selector from park or neutral into drive or reverse modes unless the vehicle brakes are applied. This ensures that the vehicle is attended by an operator and is in a safe operating mode when drive or reverse movement of the vehicle occurs.
However, the known transmission safety lock devices utilize a large number of separate parts which increases the cost of the safety lock device and makes installation more difficult. Furthermore, the number and complexity of the parts employed in such safety lock devices prevents their use on a large number of different transmissions without extensive and expensive modification of the vehicle transmission.
Thus, it would be desirable to provide a transmission safety lock device which prevent the shifting of a vehicle transmission from park or neutral into either drive or reverse unless the vehicle brakes are applied. It would also be desirable to provide a transmission safety lock device which is simple in construction and contains a small number of individual components. It would also be desirable to provide a transmission safety lock device which can easily be used with a large number of different transmissions and vehicles without excessive modification.